CA2243517C - Protecting catalysts through deposition of a protective coating - Google Patents

Abstract

A process for the passivation of a heterogeneous catalyst used for refining or hydroconversion of hydrocarbons is new. The external surface of the catalyst particles are coated with a protective layer of an inert material. Also claimed is the passivated catalyst obtained and its use in refining and hydroconversion reactions.

Description

PROTECTION OF CATALYSTS BY PROTECTIVE LAYER DEPOSITION
Heterogeneous catalysts often consist of an active phase unstable in the air. II in for example, hydrotreatment catalysts (or refining or hydroconversion of hydrocarbons) containing metallic associations CoMo, NiMo, NiW
alumina support and / or silica alumina which contain an active phase of sulphide type metallic. Another example is the hydrogenation catalysts or steam nickel-based reforming containing from 10 to 70% by weight of Ni. These same solids are also used as a sulfur trap. After reducing the NiO oxide to metal, the solid is sensitive to air, even pyrophoric. This is also true of systems based on Copper, like the Copper-Chromium for hydrogenation, Copper-Zinc for the reaction of conversion of carbon monoxide (water gas shift) in hydrogen units. there is also the iron-based catalysts in these same units (Iron-Chromium) or for synthesis of ammonia which are used after a reductive activation. In an other category, find the isomerization catalysts of n-butane or light naphtha based on Platinum and of highly chlorinated alumina for which the active phase, related to a chloride aluminum, is highly sensitive to the ambient atmosphere (oxygen and water).
The practices developed by the industry take this constraint into account.
Thus, for hydrotreating catalysts of the CoMo, NiMo or NiW type, support of preferably amorphous, the active phase is generated only after loading the catalyst in the reactor itself, under pressure of hydrogen and a sulfur compound. At the end of the cycle, the The catalyst is removed from the reactor and brought into contact with the air without produce violent reactions, because the active phase is covered with carbon compounds which limit the contact with oxygen. There may, however, be some warm-up of these catalysts when venting, due to oxidation of the sulphide phases and certain techniques have tried to solve these problems. For example, the addition of compounds polyaromatic, USP Patent 4912,071 to ICASHIMA and CHIYODA, Japan; adding of amine compounds, Nippon Mining Company patents filed in 1977 exclusively in Japan.
For catalysts based on transition metals, such as nickel, copper, Iron, the stage of Hydrogen reduction is generally also done in the unit. In some case, the reduction is carried out "off-site" in a reactant system reactor and the catalyst must be passivated to avoid any risk of overheating during transport, storage of catalyst and reactor charging. This passivation can be done from three ways different.

two The most common is superficial oxidation with air diluted by a gas inert. It is carried out very slowly increasing the partial pressure of oxygen so as to limit the elevation of temperature. This procedure creates a surface layer of oxide metallic that protects the reduced metal and thus makes it possible to handle the solid in air.
The disadvantage is that it takes again remove this layer of oxide in the catalytic reactor, in general hot. By example, if a fresh nickel catalyst is to be reduced around 400 ° C in the unit, a reduced catalyst off-site and passivated by reoxidation superficial must again be reduced in the unit to a temperature of 200-250 ° C. This imposes to have the ovens adequate upstream of the reactor. Another disadvantage is the generation of H20 corresponding to the removal of oxygen supplied during the reoxidation step. Another technical related to it is reoxidation / passivation by carbon. Finally, he is also possible to wet the catalyst with a liquid, which prevents the oxygen to diffuse in the catalyst grain. The difficulty is then to load the reactor with a mixture solidelliquide or at best a wet solid and whose grains stick together to each other.
In the case of isomerization catalysts based on chlorinated alumina, there is no no technique available passivation that can be reversible because 02 or H20 alter irreversibly active sites. The techniques employed are then to use very tight packaging for transport, such as metal drums with waterproof cover and Inert gas loading systems to limit contact with solid with traces of air or moisture.
The object of the invention is to achieve a passivation of the particles of the solid by coating the outer surface with at least one protective layer of a particular material inert and removable in the reactor under the conditions of the reaction. The heart of the solid, its porosity internal, is thus protected from the outside atmosphere by this barrier which forbids or limits the diffusion of oxygen. The originality of the invention lies particularly in the makes it a granular solid coating and not an impregnation of all the porosity of the solid. By coating means either a uniform layer of a specific thickness or a diaper whose concentration decreases from the periphery to the interior of the catalyst film, that is to say a layer whose thickness varies according to a gradient. So the concentration of the coating stretches then from the periphery to the center of the grain. The coating is carried out preferably to the outer surface of the particle and the concentration in coating material strait from the periphery to the center without the need for material in the center. The gradient, then, strait then vanishes as the center approaches.

3 More specifically, the invention as broadly described hereinafter a passivation process of a heterogeneous refining reaction catalyst or hydroconversion of hydrocarbons, the catalyst being in the form of particles with an outer surface and being used in an area reaction under given reaction conditions. According to the method, coats the outer surface of the particles of the heterogeneous catalyst of at least a protective layer of a coating material, said coating material being inert and selected from paraffins, waxes, hydrocarbons heavy oil bases, light polymers, resins, acrylic esters and polyvinyl acetate. The copolymers are used alone or in combination or diluted in a solvent. The coating material is present in amount less than about half of the filling of the pore volume and is removed in the reaction zone at the conditions of the refining reaction or hydroconversion.
The invention as hereinafter claimed, however, is more specifically intended to passivation process of a heterogeneous refining reaction catalyst or hydrocarbon hydroconversion process, characterized in that the area particles or grains of said heterogeneous catalyst of at least a protective layer of a coating material which is a liquid agent to ambient temperature and selected from the group consisting of resins in solution in a solvent and the lubricating bases used alone, under form liquid, or in solution in a solvent, said material being inert and being subsequently eliminated in the reaction zone where the said reaction will take place reaction for refining or hydroconversion of hydrocarbons, said layer being obtained by atomization or dispersion of the material on the catalyst, maintaining the stirred catalyst with formation of a protective ring or gradient, by freezing or thickening in contact with the catalyst.
Patent application EP 311 508 describes the deposition of a protective film by projection of paraffin, followed by cooling.

3a The patent application WO 94/25157 describes a protective material comprising a oxygenated hydrocarbon contacted with the catalyst at a temperature superior to the melting temperature of the catalyst.
The impregnation technique is for example mentioned in the application for WO 95 patent 398860 of 6/3/96 CHEM RES & LICENSING which mentions the anchorage by a paraffin (wax) followed by cooling. CHEVRON Patent USP 3453 217 claims impregnation with a hydrocarbon of high boiling point.
Impregnation with a compound hydrocarbon of all porosity is a process that actually allows to isolate the phase of the external atmosphere, but it has the disadvantage of require a great amount of protective material. The porous volumes of the usual catalysts being relatively high, from 20 to 80 ml per 100 g and more often from 30 to 60 ml, filling porosity will therefore generally require more than 30% by weight of hydrocarbon compound per report to solid weight. This poses different problems: high cost, density high grain which can potentially cause problems when loading the catalyst in the reactor, possible problems to evacuate this compound when starting up unit.
The coating or encapsulation according to the invention consists in filling the volume porous not of all the grain, but simply preferentially the outer ring or a gradient of grain, the objective being to deposit a quantity of protective agent equivalent, preferably, to less than about half corresponding to the filling of the pore volume, either for example less than 30%, and if possible less than 25% weight compared to solid (catalyst)..
Efficiency will obviously also depend on the permeability to oxygen (and in some cases to the water) of the material, the products being more or less efficient as material.
fence. Less permeable products may allow layers protectives more fines.
The compounds suitable for producing a protective layer are different types, and also depend on the encapsulation technique.

4 We can first coat the catalyst particles (grain, ball, extruded, or any other form solid powder) for example with a liquid while maintaining the catalyst to one below the point of crystallization (or melting) or freezing of the protective compound.
Thus a paraffin melting point 60 ° C can be atomized on a solid (catalyst) to 30 ° C and form a protective ring (or any equivalent form) crystallisation on contact cold solid (for example ambient temperature).
A polyethylene wax melting point 110 ° C may be deposited by atomization on the solid (catalyst) at a temperature of 50 to 80 ° C. Products usable in this context are hydrocarbon compounds of petroleum or synthetic origin or even natural products.
Thus paraffins or waxes or heavy petroleum hydrocarbons, light polymers like waxes of polyethylene, polypropylene, polystyrene. other weight polymers sufficiently low molecular weight to have a lower hot viscosity than 5000 centipoises (500 PascaLSeconds) (without added solvent). All existing polymers can agree if their degree of crosslinking is limited.
It is also possible to use a heavy hydrocarbon, for example a distillate under empty or a base oil. This product may advantageously be atomized hot to reduce its viscosity, on a cold solid. The temperature of the solid will not be such that the product crystallizes as in the previous cases, but such as the viscosity of the liquid in the pores become strong and slows the transport to the heart of the grain to get actually an effect coating.
Another possibility adaptable to any material mentioned above is to use a coating agent diluted or suspended in a solvent and applying by atomization, spray or Disperse the solution at a temperature above the point boiling solvent.
Thus the solvent is rapidly removed by vaporization in contact with the catalyst and solute solidified crown (or any other equivalent form) around or in the grain thus creating the protective layer.

Another possibility is to use a protective agent consisting of a set of molecules high molecular weight in solution / suspension in a solvent. Size molecules will be chosen so that their diffusion at the heart of the porosity of the solid be slowed down or

5 prevented (crown or gradient for example). So in a catalyst of diameter microporous average around 10 nanometers, as is often the case of the hydrotreating catalysts of conventional oil cuts, will be able to choose a molecule diameter greater than 10 or 20 nm, and for example 100 nm, which is the case of numerous solution / suspension polymers available on the market. All the resins used to compose the paints and varnishes may be suitable for solution / suspension in water or organic solvents. For example resins glycérophtalliques styrenics, acrylic esters, polyvinyl acetate, etc. or some copolymers. In this case protective layer consists of a continuous film of thickness for example some microns.
Among the polymeric compounds whose impermeability to oxygen is high, we find examples are: polyvinylidene chloride, ethylene-alcohol copolymer vinyl, polyamide, polyvinyl alcohol, polyacrylonitrile or polystyrene acrylonitrile, polyethylene naphthalate or terephthalate, epoxy resins, acrylic resins, Cellophane.
Some polymers are also remarkable for their waterproofness, as the polyvinylidene chloride, polychlorotrifluoroethylene. Other materials can represent a good economic compromise such as polyethylene, polypropylene, the polyvinyl chloride, etc.
Taking into account the various modes of application of the coating agent, the type of compound adequate is very broad, the only constraint being that the protective layer can be essentially removed under conditions of use of the catalyst. This compound is preferentially organic and contains carbon atoms and hydrogen with optionally heteroatoms oxygen, nitrogen, sulfur, that is to say by example of functions alcohol, aldehydes, ketones, acids, esters, amines, amides, mercaptans (thiols), sulphides, sulphones.

6 The protective layer will be removed under the conditions of use of the catalyst according to different mechanisms. For example, by dissolution in the middle reaction or by a specific solvent used for this purpose. Thus in diesel hydrotreating atmospheric or isomerization of light naphtha, these two types of filler will easily dissolve by example a paraffin layer and thus free access to the active sites of the catalyst. The product can also be destroyed by reaction under the conditions of use of the catalyst under hydrogen pressure and hot connections CS, CO, CN, CC can be partially destroyed by hydrogenolysis or hydrocracking thus allowing the destruction of the diaper protective.
This coating technique makes it possible to improve several properties of catalysts pellets, pellets or pellets 15 ~ suppression or decrease of the self-heating effect in the air, which facilitates the conditions of transport of the product. This property is evaluated by UN tests self-heating.
~ improvement of the mechanical strength of grains: formation of fines reduced when loading, pressurization and oiling. These properties are evaluated by measurement of "barrel attrition" and "crush in bed" or "Bulk Crushing Strength ".
~ improvement of the tribological properties of the grains: the grains which have resistances of reduced friction slip more easily over each other, which allows loading easier, the decrease of potential dead zones with low density of loading and so the preferential passages of the load (channeling). This property is evaluated by a flow velocity of the solid through a funnel.
These last two improvements apply equally well to a catalyst fresh, not presulfurized, prereduced or pre-treated, therefore not self-heating only on a catalyst likely to be self-heating.
In one implementation of the method of the invention, a step of venting controlled from Catalyst is carried out before passivation by coating. More particularly, the the air is operated respecting the fact that the temperature is for example less than 50 ° C
about.

7 The present invention also relates to the passivated catalysts obtained by the process of the present invention, as well as their use in deconvering processes ion hydrocarbons (particularly hydrotreatment).
Example 1 (not according to the invention) A commercial hydrotreatment catalyst containing 20% by weight of MoOa and 5%
of Co0 on aluminum support, with a surface area of 210m2 / g, is industrially presulfided by a tertiononyl polysulfide so as to obtain a quantity of sulfur of about 90% of the theoretical stoichiometry of MoS2 and CogSg sulphides.
The following table summarizes the physicochemical characteristics obtained.
Some methods are detailed below.
The catalyst obtained is subjected to a self-heating test to determine his belonging to class 4.2 self-heating materials according to the norm UN: 15.5 cc of catalyst are placed in a 2.5 cm grid cube. The mesh roasting is 0.5 mm. In the center of the cube a thermocouple measures the temperature. The cube is introduced in an oven at 140 ° C and the temperature at heart is followed during the time. The auto character heating in the sense of the norm is positive if after 24 hours of testing, the temperature to heart exedes 200 ° C.
The pore volume is defined by the maximum amount of water adsorbed by the catalyst to saturation of this (in ml of water per 100 g of catalyst).
The attrition test, severed version of ASTM D4058 by increasing time of test at 3 o'clock, measures the mechanical strength of the grains subjected in mass to falls repeated in a barrel. Attrition is given by the percentage weight of lower fines at 0.5 mm produced during the rotation of the catalyst in the cylinder turning.
The BCS ~ Bulk Crushinq_Strength) classifies the resistance to crushing by the measurement of a pressure of a piston exerted on a bed of solid, which pressure generates 0.5% wt of fines from dimension less than 0.5 mm and is expressed in MegaPascals.
Weight loss measures the percentage decrease in a mass of calcined catalyst muffle furnace at 500 ° C for 4 hours.

8 The flow rate of the catalyst is defined from a time necessary for emptying total of 3 liters of catalyst through a 14.6mm2 circular orifice section and is expressed in liters per minute.

Catalyst prsulfur, basic case.

Weight loss (%) 183 Carbon (% wt) Sulfur (% wt) 8.1 Densit cup (kg / cm3) 0.86 Bulk Crushing Strength (Mpa) 1.0 Attritiort (% wt) 1.4 Positive self-heating characteristic Temp. maximum UN test (C) 445 Porous volume (m1 / 100 g) 23 Flow rate (I / min) 1926 The catalyst must be classified as self-heating, given its test behavior UN.
Example 2 The sulfurized catalyst as obtained in Example No. 1 is introduced in a steel barrel in rotation at 100 rpm. The barrel is equipped with 4 lifters ensuring the permanent brewing of catalyst Iws of rotation and a nozzle for compressed gas spraying (gun type painting). The whole is heated to 50 ° C.
A solution containing 20% by weight of acrylic polymer type resin in acetate of ethyl, is slowly sprayed onto the catalyst so as to deposit 5 g of polymer for 100 g of catalyst over a period of one hour. The molecular size of the polymer acrylic (> 100 nm) is greater than the size of the micropores of alumina (10 nm). The setting of the nozzle is made of so that the vector solvent is virtually completely vaporized during from the trip to catalyst grains. The polymer is deposited randomly on the outer surface of continuous brewing catalyst particles, preventing any agglomeration by collage and creating thus a protective layer on all sides and infractuosities of each elementary grain.

9 Various types of analysis and experimentation are then carried out. They are summarized in the table below and explained below.
Prsulfur Enrob Enrob / Enrob /
(without enronage) (Lixivi / SchConcass product finished) Weight loss (9 ') 18.3 23.2 14.2 -Carbon (% by weight) 7.7 10.3 5.0 -Sulfur (% by weight) 8.1 7.5 7.5 -BCS (MPa) 1.0 1.3 - -Attrition (% wt) - 0.5 - -Porous volume (m1 / 10023 5.7 27 19.5 boy Wut) Positive negative self heating characteristic -Temp. Max Test 445 155 325 -UN (C) Flow rate1926 2022 - -(I / min) Subject to the same self-heating test as in Example 1, the catalyst coated does not reach 155 ° C attesting the disappearance of the character of self-heating by external protection (see table above). The pore volume with water is reduced to 25% of the value initial example 1 and attests to the development of a barrier between the outside and the heart of the grain. The coated catalyst is then partially broken up by crushing so as to reduce the length half of the grains thus discovering an uncoated surface. The porous volume impregnation with water goes back to 84% and proves that only the surface grain was protected. Low attrition (0.5% fines after 3 hours) and BCS
(1.3 MPa) testify to the improvement of grain strength properties of grain constraints such as those encountered during reactor shipments industrial or pressure surges during the start-up period.
Then we wanted to check that it was the coating that gave the produces the loss of self heating character. So this coated catalyst is subjected to a wash at hot toluene (Soxhlet technique) for 2 hours. The leachate obtained is parboiled at 120 ° C, it leaves a an elastic film-forming residue composed of polymer and organic residues. After drying 3 h in a thin layer at 120 ° C. in a ventilated enclosure, the catalyst is tested again in auto-warming up. The temperature rises to 325 ° C and certifies the recovery self-character warming. The impregnation volume amounts to 27 ml or 118% of the value basic. Therefore by removing the protective layer, the pore volume is increased with water and find the self heating character. _ To confirm the concept of protective layer, we have also roughly crushed them coated catalyst grains to shorten the average length of half. Volume porous measured on these grains, thus presenting at least statistically a pseudo section 5 circular free of barrier polymer, goes back to 19.5 ml showing that access to porosity is partially returned by the broken faces and thus uncoated.
Example 3

100 g of the initial oxide catalyst of Example 1 are sulfurized in a fixed bed in a vertical oven at 350 ° C under hydrogen / hydrogen sulfide mixture (H2 / H2S - 85/15 volume / volume) debiting at 40 I / h under atmospheric pressure. The duration of the landing is 1 hour then the catalyst is cooled to room temperature under nitrogen.
The sulphurized catalyst is brought into contact with the air at the rate of 5 steps successive one-hour partial pressures of increasing oxygen in the following series: 0.5%, 1 %, 5%, 10%, 20%, respecting the fact that the temperature remains below 50 ° C.
The product is deposited in a rotating steel barrel in which atomizes at 160 ° C
a polyethylene wax with a melting point of 137 ° C. In contact with solid cold, the wax is solidifies the surface of the porosity of the grain and the amount of wax deposited corresponds to 8 weight relative to the catalyst.
The same methodology as in the previous examples is used, namely:
analyzes of the sulphurized catalyst, coated catalyst, and then coated catalyst leached with heptane to heptane.
Sulfur Enrob Lixivi / sch Weight loss (%) 5.1 12.9 4.1 Carbon (% wt) 0.1 5.5 1.3 Sulfur (% by weight) 9.5 9.1 9.3 BCS (MPa) 1.1 1.3 1.1 Attrition (% wt) 1.5 0.8 1.2 Porous volume (m1 / 10048 4.2 43 boy Wut) Self-Heating Character Positive Ngative Positive Temp. Max Test 410 155 425 UN (C)

11 The coated solid is no longer self-heating, but becomes so again if the wax is removed by leachate with hot heptane. The porous volume also follows the same trends and mechanical properties are also improved by coating Example 4 A sulfurized catalyst according to Example 3, not subject to mild oxidation passivating in the air, receives a spray, under an inert atmosphere at 120 ° C, base oil type 600 Neutral (TOTAL origin, viscosity at 40 ° C: 120 centipoise). The amount of oil deposited represents 20 weight of solid ~ coated.
After cooling to room temperature and re-airing, the coated catalyst is subject to following treatments Prsulfur Enrob Enrobl Enrobl (base) (LixivilSchConcass product finished) Weight loss (% NA 20.1 8.5 -w) Carbon (% wt) 0.3 15.5 2.4 -Sulfur (% by weight) 9.8 8.7 9 Porous volume (m1 / 10047 10 39 30 boy Wut) Self-Heating Character Positive Ngative Positive -Temp. maxi Test NA 160 C NA -UN (C) Like the previous examples, we note the disappearance of the character self-heating and a partial blockage of the external porosity of the coated catalyst. The coating is eliminated by solubilization in toluene.
Example 5 (non-compliant) The example is carried out on a commercial catalyst containing 75% by weight nickel oxide (Ni0), used for hydrogenation reactions. 80 g of this product is loaded into a vertical glass reactor and reduced to fixed bed under hydrogen at 450 ° C
for 2 hours, then cooled under nitrogen.

12 The reactor is then transferred to a glove box filled with nitrogen and its emptied content in a Dewar vase. This one is then out of the box and thus abruptly exposed to the air.
The internal temperature of the catalyst is followed by a thermocouple; this one mounted abruptly up to 175 ° C.
Example 6 The same methodology as in the previous example is used, except that the catalyst is going be coated after reduction as follows: in the glove box under nitrogen content reactor (the catalyst reduced to 450 ° C under hydrogen) is emptied into a steel barrel and heated to 60 ° C by an infrared lamp. A solution at 20% weight of polymer type resin acrylic in ethyl acetate is vaporized on the rotating solid of such way to drop 10% resin. The product is allowed to rotate for drying during a hour and then cooled one hour and submitted to the DEWAR test as in the previous example. Temperature internal when released to air passes from 27 to 35 ° C, which proves that the oxidation reaction was extremely limited because of the protective polymer layer slowing down the diffusion of oxygen.

Claims (10)

1. Process for passivating a heterogeneous reaction catalyst of refining or hydroconversion of hydrocarbons, characterized in that one coats the outer surface of the particles or grains of said catalyst heterogeneous at least one protective layer of a coating material which is a liquid agent at room temperature and chosen from the group consisting of by the resins in solution in a solvent and the lubricating bases used alone, in liquid form, or in solution in a solvent, said material being inert and subsequently removed in the reaction zone where place said hydrocarbon refining or hydroconversion reaction, said layer being obtained by atomization or dispersion of the material on the catalyst, now the catalyst with stirring, with formation of a protective ring or a gradient, by freezing or thickening in contact with the catalyst. 2. Method according to claim 1, wherein the material is present in an amount of less than 30% by weight. 3. Method according to claim 2, wherein the material is present in an amount of less than 25% by weight. The method of any one of claims 1 to 3, wherein material is a Neutral type oil base. The method of any one of claims 1 to 3, wherein said material is an acrylic polymer type resin. The method of any one of claims 1 to 5, wherein the coating of the particle has the shape of a crown or present appearance of a gradient. 7. Process according to any one of claims 1 to 6, characterized what ::

a) the material is atomized or dispersed over the catalyst while maintaining the catalyst with stirring and at a temperature below the crystal point.
materialization, b) a protective ring or gradient is formed by freezing or thickening in contact with the catalyst. 8. Process according to any one of claims 1 to 6, in that:

a) atomizing, spraying or dispersing the solution containing the material now the catalyst with stirring and at a temperature above boiling point of the solvent.

b) the protective layer is formed by depositing the solute around the crown, around or in the catalyst grain. 9. A passivated catalyst obtained by the process according to any one of Claims 1 to 8. 10. Use of a catalyst according to claim 9 or prepared by the process according to any one of claims 1 to 8 in a reaction of refining or hydroconversion of hydrocarbon feedstocks.